Heat your oven to 220°C/Fan 200°C/Gas 7. Place your sweet potatoes on a chopping board. Use a sharp knife to make deep slices into each potato around 1 cm apart. Take care not to cut all the way through – the base needs to hold the potatoes together.
Pop the potatoes on a baking tray. Drizzle each one with ½ tbsp oil, allowing the oil to run into the cuts. Season generously. Roast for 40 mins till crisp and golden. Crumble the stock cube into a heatproof jug. Stir in 300ml boiling water.
Peel and finely chop the onion. Peel and crush the garlic. Finely chop the tomatoes. Halve the chilli, then flick out the seeds and white bits. Finely chop half the chilli and save the other half for later.
Warm a pan for 1 min over a medium heat. Add ½ tbsp oil and the onion to the pan. Cook and stir for 5 mins till softened. Add in the beef mince, breaking it up with the spoon. Cook and stir on a high heat for 5 mins till the beef is browned.
Sprinkle in 2 tsp of the Cajun seasoning. Scrape in the garlic, chopped chilli and chopped tomatoes. Cook and stir for 2 mins. Pour in the stock. Cover and simmer for 20 mins.
While the beef is cooking, finely slice the remaining chilli half for garnishing. Cut the lime into wedges. Drain and rinse the mixed beans.
After the beef has cooked for 20 mins, tip in the beans. Cook for a further 10 mins. The potatoes should now be ready, with crisp skins and fluffy flesh. Taste the beef chilli and add more salt, pepper or Cajun seasoning if you think it needs it.
Place the potatoes onto two warm plates. Spoon over the chilli. Dollop on the soured cream. Sprinkle over a little Cajun seasoning and the sliced chilli. Serve with the lime wedges for squeezing.